I got that problem too when I first got this pack. For myself, I found that it was my vehicles.meta entries. You can install police6 with no issue, but when you add police7 vehicles.meta entry, it crashes the game. You need to keep the 4 lower spaces empty at the bottom of your police7 meta entry. This will always be at the bottom between "</Item>" and "</InitDatas>". Try keeping the 4 lines of blank space between the two mentioned texts. That worked for me. If this works, make sure to do the same thing for police8, 9 and so on.
Do I have to reinstall this dlc pack?
I am in no way an expert in modding, only through tutorials on youtube. I installed this pack before GTA's 1365 update (on 1290), and it worked perfectly. Installed several police add-on cars and that was it. Once GTA updated to 1365, all I did was get a new gameconfig from F7YO, and the game worked fine without crashing; but now, all my add-on cars are unavailable. In OpenIV, I can see that modding dlc is still installed with my add-on car files still there, but using the trainer, they are unavailable. Slots are disabled.
How do I fix this?